That was my first thought, but it didn't make much sense to me. Maybe my understanding of scoping isn't quite as good as I thought, but I thought that you had to declare a variable outside of the scope of the sub in order to create a closure.

Could it be that the one-time compilation of the regex somehow causes the closure?

Also, saying local $ret = ''; breaks under strict:

Variable "$ret" is not imported at /home/apirkle/bin/retest.pl line 8.
Global symbol "$ret" requires explicit package name at /home/apirkle/b
+in/retest.pl line 6.
Global symbol "$ret" requires explicit package name at /home/apirkle/b
+in/retest.pl line 8.
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